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51.
LI Yan-Tuan LIAO Dai-Zheng JIANG Zong-Hui WANG Geng-LinDepartment of Chemistry Nankai University Tianjin China 《中国化学》1995,(3)
Six novel μ-oxamido heterobinuclear complexes, namely Cu(oxae)Ln(Me2bpy)2-(ClO4)3 (Ln=La, Nd, Gd, Tb, Ho, Er), where oxae denotes N, N'-bis(2-aminoethyl)oxamido dian-ion, Me2bpy is 4,4'-dimethyl-2,2'-bipyridyl, have been synthesized and characterized by elemental analyses, IR, conductivity measurements and electronic spectra. The temperature dependence of the magnetic susceptibility of Cu(oxae)Gd(Me2bpy)2(ClO4)3 has been meaured over the range 4-300 K. The least-squares fit of the experimental susceptibilities yielded J - 1.87 cm-1.The observed Gd(Ⅲ)-Cu(Ⅱ) coupling is ferromagnetic. One plausible mechanism that can cause a ferromagnetic coupling between Gd(Ⅲ) and Cu(Ⅱ) is discussed in terms of spin-polarization. 相似文献
52.
P. Elumalai H. N. Vasan N. Munichandraiah 《Journal of Solid State Electrochemistry》1999,3(7-8):470-473
Charge-transfer resistance [R
ct = (dη/di)η = 0] and Tafel plots of current density (i) versus overpotential (η) data are generally known to yield values of the energy-transfer coefficient (α) and exchange current
density (i
o) of an electrochemical reaction. In the present investigation, the resistance (dη/di)η≠0 that could be calculated by differentiating a wide range of i−η curves was also shown to provide the values of α and i
o, by plotting ln(dη/di)η≠0 against η. Since α and i
o could also be evaluated directly from the experimental DC polarization data, the procedure was not of significant importance.
Nevertheless, it was considered important in evaluating α and i
o from AC impedance data, because the procedure was based on data analysis, which was much simpler than that reported in the
literature. A cobalt electrode prepared from fine metal powder was used in 1 M KOH electrolyte and the hydrogen evolution
reaction was studied by AC impedance at several potentials. The resistance values measured from the complex plane impedance
diagram were plotted against the potential, and the values of α and i
o were evaluated.
Received: 8 October 1998 / Accepted: 11 January 1999 相似文献
53.
Johannes Müller Janina Buck Prof. Dr. Andreas Hirsch 《European journal of organic chemistry》2023,26(9):e202201310
Within the scope of this paper, nine π-expanded mono-substituted 5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronenes (HBC) are introduced. 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronene served as precursor and was reacted with ethynyltrimethylsilane in a Sonogashira coupling reaction. The acetylene unit is used as a linker and can undergo another Sonogashira coupling reaction combining different phenyl coupling partners with the HBC core. The electron-withdrawing groups such as nitrile, pyridine and carbonyl species (aldehyde, methylester, carboxylic acid) as well as the three quinoxaline based species (diphenylquinoxaline, dibenzo[a,c]phenazine, phenanthro[4’,5’-a,b,c]phenazine) serve as substitution moieties. Their influence on the optoelectronic properties were investigated by UV/Vis absorption spectroscopy demonstrating a maximum redshift of 7 nm compared to starting compound 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl) HBC. As for the phenanthro[4’,5’-a,b,c]phenazine substituted HBC a dramatic decrease in the intensity of the absorption of the UV/Vis spectrum was observed. The fluorescence spectroscopy pointed out that the dibenzo[a,c]phenazine and phenanthro[4’,5’-a,b,c]phenazine substitution changed the spectra to one broad peak departing from the characteristic HBC-like emission pattern. 相似文献
54.
A composite film consisting of poly(o-phenylenediamine) (PoPD) and poly(vinyl alcohol) (PVA) has been prepared, and the effect of the protonation level of PoPD on the response of the composite to humidity been investigated by ac impedance measurements. The electrochemical system of the PoPD/PVA composite in a humid atmosphere is represented by an electrochemical equivalent circuit containing film (Rfilm, Cfilm), Warburg (W) and interfacial (Rct, Cdl) impedance. Rfilm was increased with decreasing protonation level of the PoPD in relative humidity regions higher than 40%, but it was almost independent of the protonation level in humidity regions lower than this percentage. 相似文献
55.
《Arabian Journal of Chemistry》2020,13(2):4126-4133
Three biscoumarin dyes bridged by polycyclic aromatic bridges (anthracen, pyrene and dibenzo[g,p]chrysene) were prepared as the emissive materials for the application of organic light-emitting devices. The relationship between their structures, photophysical properties, electrochemical properties and performances of organic light-emitting devices are described. The multilayered doped devices with a configuration of ITO/NPB (20 nm)/TBADN: biscoumarin compound (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method. All the devices showed green emission with high electroluminescent efficiencies. Especially, the device based on the compound containing pyrene as a bridge group at 7% doping concentration showed the best performance with a maximum brightness of 10552 cd/m2, maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency (EQE) of 2.35%. 相似文献
56.
Three new binudear cobalt (II) complexes with extended te-tracarboxylato- bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA) (NO2phen)4] (3), where PMTA represents the tetraanion of pyroniellitic acid, and bpy, phen, NO2-phen denote 2,2'-bipyridine, 1,10-phenan-throline; 5-nirto-1, 10-plienanthroline, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have PMTA-bridged structures and consist of two cobalt (II) ions, each in a distorted octahedral environment. These complexes were further characterized by variable temperature magnetic susceptibility measurements (4-300 K) and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, giving the exchange integral J = - 1.02 cm-1 for 1, J = -1.21 cm-1 for 2 and J = - 1.18 cm-1 for 3, respectively. These results revealed the operation of antiferromagneti 相似文献
57.
58.
采用浸渍法制备了分别以活性炭(AC)和全硅MCM-41介孔分子筛负载的ZrO2催化剂,并对其进行了XRD、氮气吸附-脱附、X射线光电子能谱、差热-热重分析和吡啶吸附原位红外光谱等表征,考察了其在以异丙醇为氢源还原苯乙酮为α-苯乙醇的Meerwein-Ponndorf-Verley(MPV)反应中的催化活性,并与水合ZrO2进行对比.研究了载体对催化剂活性的影响.结果表明,ZrO2经MCM-41负载后,与载体发生强相互作用,可能形成Si—O—Zr键,ZrO2在载体表面呈高分散的无定形态,Zr—OH数目显著增加,L酸性增强,并形成B酸中心,使催化剂活性显著高于水合ZrO2;ZrO2负载在AC上后,与载体未发生强相互作用,ZrO2在载体表面未呈高分散状态,增加的Zr—OH数目相对较少,L酸性较弱,未形成B酸中心,催化活性未明显增加,但在较高焙烧温度(400~600℃)下,其仍能保持稳定的催化活性,这可归因于ZrO2/AC中AC孔道疏通及AC石墨层对苯乙酮上苯环的吸附作用,使活性位附近的反应底物浓度显著增大. 相似文献
59.
用浸渍法制备了掺杂不同质量分数的La0.8Sr0.2Ga0.8Mg0.15Co0.05O3-δ (LSGMC5)粉末的Ni8-Fe2-LSGMC5复合阳极, 并采用交流阻抗和直流极化技术考察了以氢气和二甲醚为燃气时该复合阳极的电化学性能及相应电池的功率输出特性. 结果表明, 在电极中掺入LSGMC5 粉末, 能显著地改善电极的形貌和电极/电解质界面结构, 减小欧姆电阻和极化电阻. 电极中LSGMC5 粉末含量对于氢气及二甲醚电化学氧化性能的影响显著不同. 以二甲醚为燃气时, 电极极化电阻随LSGMC5 粉末含量的增加而减小, 其中LSGMC5 掺杂量为30%的复合阳极具有最高的电化学性能, 相应电池在1073、1023、973 K 时的输出功率分别为1.00、0.61、0.40 W·cm-2; 以氢气为燃气时, LSGMC5 掺杂量为20%的复合阳极具有最好的电化学性能, 随着LSGMC5 掺杂量的进一步增加, 电极极化电阻显著增大. 相似文献
60.